Recently, there are many cases that operation menus and the like are superimposed on pictorial images which constitute backgrounds and displayed. In order to apply high quality feelings, or high grade feelings to object images such as these menus, not only simple switching operations of displaying, or not displaying these object images are carried out, but also transition conditions must be made smooth, during which these object images are switched from being displayed and not being displayed, and vice versa. In the case that such a transition condition is formed by way of a drawing operation, since images are required to be re-drawn with respect to each of frames, lengthy time is required.
A processing flow operation proposed in a related art is shown in FIG. 1B. A pictorial image is drawn by a drawing process unit 11. The drawn image data is stored into a predetermined storage position of a memory 13. When an image is to be displayed, the image data is read out from a predetermined storage position of the memory by a memory control unit 16. This memory control unit 16 operates as an image processing/synthesizing unit. Then, such a processing operation as an RGB converting operation and a simple image synthesizing operation is carried out with respect to the read image data by a display processing unit 15. Thereafter, the processed image data is outputted to a display device 17 at necessary timing. While the memory 13 is constituted by, for example, a VRAM (video random access memory), the display processing unit 15 sequentially reads out the image data along the raster direction to execute the display processing operation with respect to this memory 13.
When an image to be displayed is changed, this image is re-drawn by the drawing unit 11 and then, the re-drawn image is stored in the memory 13. Then, the memory control unit 16 reads out this stored image data if required, and executes such a processing operation as the affine transformation with respect to the read image data. Thereafter, the processed image data is stored in the memory 13. In the case that an image processing technique which is typically known as the affine transformation is carried out, there are many possibilities that addresses of read pixels are different from calculated addresses. As a result, while an additional memory used to save images is separately provided, the following operation is carried out. That is, a calculation result obtained from the read pixel values is stored in a calculated address of the additional memory.